If there be a noticeably greater excess of volunteers over men needed in any trade, it is inferred that the trade offers greater attractions than others.

On the other hand, if the number of volunteers for a trade tends to drop below the demand, it is inferred that it is thought more arduous.

It is the business of the administration to seek constantly to equalize the attractions of the trades, so far as the conditions of labor in them are concerned, so that all trades shall be equally attractive to persons having natural tastes for them.

This is done by making the hours of labor in different trades to differ according to their arduousness.

The lighter trades, prosecuted under the most agreeable circumstances, have in this way the longest hours, while an arduous trade, such as mining, has very short hours.